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This hand-held instrument combines several different functions including singlechannel CAT III oscilloscope, CAT III multimeter, data logger, 8-channel logic analyser with protocol decoder and pattern generator in one hand-held, batterypowered instrument. If you can only carry around one instrument in the field, this one’s for you. WENS 540 Debug Meter C ontinuing the trend of combining multiple functions into one test instrument, this is a step closer to “nirvana” where one device does everything. Sometimes that means making a lot of compromises but in this case it seems that the manufacturer (WENS) has struck a fine balance of functions, convenience and performance. The WENS 540 is a little bigger than your average multimeter, at 100mm wide, 220mm high and 54mm deep. It weighs 800g so it isn’t difficult to hold or carry for short periods. It’s certainly much more convenient than the larger portable scopes which are definitely two-handed affairs. The built-in tilting stand makes it also convenient for desktop use. WENS haven’t cut corners on the multimeter, as can sometimes happen with multi-purpose instruments. The functions include DC volts (50mV-1000V), AC volts (50mV-1000V True RMS), or AC+DC volts (500mV-1000V True RMS), AC, DC or AC+DC current (500A-10A), resistance (50- 50M), continuity, diode test, capacitance (5nF-500μF) and frequency/ duty cycle (100kHz-3MHz). It can also display temperature if a thermocouple is connected (not supplied). In DMM mode, it has a large 50,000 count display. Thus the finest resolution available in each mode is 1μV for voltage, 10nA for current, 1mfor resistance, 1pF for capacitance and 1Hz for frequency. In many modes there is also a bar graph display so you can see rapid changes in the readings. It also has min/max/ average display, peak hold and auto or manual ranging, plus some intriguing features we haven’t seen in other devices, such as a ripple voltage or ripple current measurement up to 100kHz. Overall reading accuracy is quite good, at ±0.025%+10 counts for most voltage readings, ±0.15%+10 counts for most current readings, ±0.05%+30 counts typical for resistance and ±1%+10 counts for typical capacitance readings. In terms of features and accuracy then, it’s comparable to a good quality mid- to upper-range dedicated multimeter. And like some of the more expensive multimeters it also Review by Nicholas Vinen siliconchip.com.au December 2014  61 has a data-logging mode, where it stores up to 10,000 measurements. You can then download these measurements to a PC via the USB connector. But because of the graphical LCD, you can actually do quite a bit of analysis on-screen if you prefer. Oscilloscope mode Even though it only has a single channel and lacks the colour screen of a dedicated DSO, the oscilloscope functions of this device are better than you might expect from such a small unit. It has 10MHz bandwidth and does up to 50 megasamples per second. Inherent noise is low and the screen is updated many times per second. The sensitivity range is quite wide, from 20mV/div to 100V/div. There’s no “probe” attenuation since the inputs are banana sockets, so this whole range is usable. Noise is low, even at maximum sensitivity. Input coupling is AC or DC and there are two acquisition modes, sampling or peak. Trigger options are Edge or Pulse and can be set for rising/ falling/alternate/either edge and positive/negative pulses. Trigger modes are Auto, Normal or Single. A number of measurements are available including mean and RMS voltage, frequency, period, pulse widths, peakto-peak voltage, minimum and maximum voltage and total amplitude. Up to four measurements can be displayed and there are also manual cursors available. The unit’s memory is only 1kpoints so basically, you can freeze what you see on the screen and that’s about it. Still, it’s quite useful for such a small unit. Logic and protocol analyser The logic analyser “head” provided is great since it is easy to plug in and has multiple, colour-coded, permanently attached “IC clips” at the other end of a decently long cable. While logic heads with detachable clips have some advantages, they have the distinct disadvantage that if you bump your set-up they can come loose, so these ones get a thumbs-up. The main cable connector is basically a standard pinheader socket with some pins missing so you could easily make up a cable to connect the unit to a row of test headers on a PCB, which we think is a nice touch. Regarding the supplied cable, in addition to the eight logic channel clips (blue), which are labelled with their channel number (nice!) and black ground clip, there are red and black alligator clips for the adjustable square wave output (10Hz-1MHz, 5V fixed amplitude, 5-95% duty cycle) and the transmit/receive IC clips (red) for the pattern generator. The pattern generator is used primarily to inject a 3.3V serial stream into the device under test (DUT) using logic-level serial (RS-232), CAN or some other arbitrary serial bus and then observe and decode the response on another signal line. You can store up to eight patterns in the device and the signal polarity is selectable. The display shows any serial data received while transmitting the selected pattern. We would have liked some other protocol options such as I²C and SPI but that would require more than one output line. As it is, this could definitely be a useful feature, especially if you are trying to debug a device in the field which has a serial configuration interface (a pretty common situation). Getting back to the logic analyser itself, it can operate on signals up to 10MHz (with a sampling rate of 50MHz) and also has a 1kpoint memory (per channel). It can handle sig62  Silicon Chip Supplied accessories include the carry case, probes as shown (including 14-way clip leads), a USB cable and an approved plugpack/charger. There’s a range of optional accessories available to suit specific tasks. nals up to 10V and the low/high threshold is around 0.7V (ie, one diode drop) so it’s suitable for use with just about any low-speed signalling scheme. The protocol analyser (supplied as standard) can decode many different kinds of serial signals including CAN, LIN, I²C, UART, USB (low/full speed), I²S, SMBUS, SPI, DMX512 and Dallas 1-Wire. That’s a comprehensive list. Trigger options depend on the serial bus being decoded. For example, for USB, you can trigger on start of packet (SOP), end of packet (EOP), reset complete (RC) or entering or exiting suspend mode. You can’t choose which logic channels go where, but it does show you how to hook it up. For example, in SPI mode, probe one goes to MISO (Master In, Slave Out), probe two to MOSI, probe three to SCK (clock) and probe four to SS-BAR (Slave Select, active low). The remaining channels can then be used to monitor any other digital signals in the circuit you may be interested in. These can also be used to trigger the logic/protocol analyser, if you don’t want to trigger on serial bus events. Some of the decoders have extra options, for example, in SPI mode you can change the clock polarity and there are a few different SPI variants such as “Microwire” which are also supported. Overall this is a pretty flexible logic analyser, with the main limitation being that there is no mixed signal mode, ie, you can’t use the scope and logic/protocol analyser functions simultaneously. PC software The supplied Windows software works well – see the accompanying screen shot. It shows a live view of the device’s screen, so you can save images and so on. You can also control the device, with a similar interface to the unit’s own buttons and you can easily start and stop logging data and then save that data to your computer. It’s basic but it’s a fast, no-fuss way to get data off the device. The unit is powered from a build-in rechargeable NiMH pack and is charged using an Australian-made approved plugpack (supplied). Battery life is good and based on our siliconchip.com.au experience, the claimed eight hours on a single charge is plausible. They do not give a figure for shelf life though. If it’s a low self-discharge type NiMH pack then it should hold its charge for several months (even with occasional use) but we didn’t have the unit for long enough to test this out. Conclusion Overall, the WENS 540 is easy to drive and if you’re reasonably familiar with other test equipment, you’ll figure it out after just a few minutes of use. As a multimeter, it works well and is similar enough to other meters that just about anyone can pick it up and use it. As a scope, its functions are quite simple but nonetheless useful. Boot-up time is quick; it only takes a second or so to switch on and be ready for use. The WENS 540 is supplied with a number of standard accessories including probes (decent quality), the logic “head”, mains charger, USB cable, multi-compartment carrying case with shoulder strap, user manual and software/documentation CD. . . basically, everything you need. So in a nutshell, if you need a test instrument that you can easily carry around with you, or you don’t already have much test equipment and want to buy a single unit that will serve you well in a variety of different test and debugging situations, the WENS 540 would be a good choice at $795 + GST. If you do a lot of field servicing or even at a workbench, there are certain advantages to a unit like this: less clutter, more room to work with the device under test, easier to move around (no mains cord) and so on. In fact, if you carry around the WENS 540 and a good LCR meter with ESR and impedance measurement, you can do Wabeco Australia wabeco.com.au deals<at>wabeco.com.au The Windows-based software supplied allows live control and logging over USB. Stored waveforms and screenshots can be transferred to the PC this way. just about any electronic test or measurement you might possibly need out in the field, with room left in your glove box. For more information To purchase one of these units, or even if you’d like more information, contact Trio Test & Measurement on 1300 853 407, e-mail sales<at>triotest.com.au or visit www.triotest.com. au/shop/en/237-handheld SC German made Highest precision 5 year warranty 5% discount for all SILICON CHIP readers unti 30-Apr-15 Wabeco D6000 Lathe 90-10601 $8,949 $8,499 High speed version available Camlock version available CNC version available Ball screws available Accessories available Price is correct at time of printing but subject to change without notice due to exchange rates. siliconchip.com.au December 2014  63